Sears Cook Walker

Background

Sears Cook Walker was born in Wilmington, Massachussets, the son of Benjamin Walker and Susanna (Cook) Walker, and a brother of Timothy Walker. The devotion of his mother guarded his childhood after the death of his father in 1811.

Education

His mother directed his education in preparation for entrance into Harvard College. For a decade he graduated from Harvard College in 1825

Career

He taught school near Boston and in Philadelphia, whither he removed in 1827. During this period he acquired an astronomical clock, a twenty-inch transit instrument, and a small Dollond telescope; and from about 1836, when he gave up his school to become actuary to the Pennsylvania Company for Insurance on Lives and Granting Annuities, his leisure hours were devoted to astronomical observation and study. In 1837 he founded one of the first astronomical observatories in the United States in connection with the Philadelphia High School and imported from Munich superior instruments of observation. He then began to make extensive contributions to the Proceedings and Transactions of the American Philosophical Society and to astronomical journals, concerning the observations made at his observatory and including a large body of observations of occultations of stars by the moon; as early as 1834 he had prepared parallactic tables which greatly reduced the time required to compute the phases of an occultation. But he made his recognized entrance into the ranks of scientific investigators, on January 15, 1841, when he read a brilliant memoir on "Researches Concerning the Periodical Meteors of August and November, " before the American Philosophical Society. In 1845 he accepted a position in the astronomical staff of the United States Naval Observatory in Washington, D. C. , and in 1847 advanced the prestige of this newly founded institution by his announcement, on Feburary 2, 1847, that the planet Neptune, which had been discovered on September 23, 1846, was identical with a star seen twice by Lalande in May 1795, and which had been referred to as fixed star No. 26266 in Lalande's catalogue. His researches in this relation enabled him to determine the orbit of Neptune thus early after its discovery. From 1847 until his death, Walker was in charge of the computations of geographical longitude in the United States Coast Survey. His discussion of the largest collection of observations of moon culminations and occultations ever made in America, undertaken with the object of determining the longitude of a central datum point for American surveys, led to the conclusion that longitudes deduced from moon culminations could not be reconciled with those from occultations. His examination of the theory of these observations, in the course of seeking for an explanation of the discrepancies which his discussion had revealed, led him to break sharply with traditions of long standing and gave weight and finality to his conclusion that the new electric telegraph furnished the best means for determining the difference of longitude from place to place, and hence the longitude of any certain place from a prime meridian. The telegraphing of transits of stars was original with him, as was also the application of the graphic registration of time-results to the registry of time-observations for general astronomical purposes. This system came to be known as the American method. On October 10, 1846, the transit of a star was telegraphed by the Naval Observatory to Philadelphia. As Walker stated before the American Association for the Advancement of Science, "this was the first practical application of the method of star-signals, which is sooner or later to perfect the geography of the globe".

Achievements

• He was among the first to make use of the electric telegraph for the purpose of determining the difference of longitude between two stations, and he introduced the method of registering transit observations electrically by means of a chronograph. He also investigated the orbit of the newly discovered planet Neptune.

Works

More photos

• book

  • The New Latin Reader: Containing The Latin Text For The Purpose Of Recitation; Accompanied With a Key, Containing The Text, a Literal And Free ... Latin And The English Idioms (Latin Edition)

    (Excerpt from The New Latin Reader: Containing The Latin T...)

  • A Treatise On Astronomy

    (This book was originally published prior to 1923, and rep...)

  • The New Latin Reader: Containing the Latin Text for the Purpose of Recitation. Accompanied with a Key Containing the Text, a Literal and Free ... Between the Latin and the English Idioms ..

    (This is a reproduction of a book published before 1923. T...)

Membership

He was elected a member of the American Philosophical Society in 1837.

Interests

• Walker learned to read at least seven languages.

Connections

Father:

Benjamin Walker

Mother:

Susanna (Cook) Walker

sibling:

Timothy Walker